The prior art has employed many devices and systems to process and purify water from industrial operations and municipal sources prior to discharging the water. Wastewater treatment plants (WWTP's), which are well known in the art, have been most often utilized to address this problem. Additionally, many industrial and municipal water treatment plants utilize biological systems to pre-treat their wastes prior to discharging into the usual municipal treatment plant.
Microorganisms used in the sludge break down or degrade contaminants for the desired water treatment in these processes. Efficient process performance and control requires quick and accurate assessment of information on the activity of the microorganisms. This has proven to be a difficult task in view of the wide variety of materials and contaminants that typically enter into treatment systems. Also, variations in the quantity of wastewater being treated, such as daily, weekly or seasonal changes, can dramatically change numerous important factors in the treatment process, such as pH, temperature, dissolved oxygen, nutrients and the like, alteration of which can be highly detrimental to proper wastewater treatment. Improperly treated wastewater poses serious human health dangers.
Various biological nutrient removal (BNR) processes are often used in biochemical systems/plants/processes. "BNR" is used hereinafter in a very generic sense, namely any biochemical process that uses microorganisms to remove nutrients. In BNR processes, contaminants in liquids such as wastewater, particularly carbon sources (measured as biochemical oxygen demand or BOD), ammonia, nitrates, phosphates and the like are digested by activated sludge in anaerobic, anoxic and aerobic (oxic) stages, also known in the art. In the anaerobic stage, wastewater, with or without passing through a preliminary settlement process, is mixed with return activated sludge (RAS), sometimes hereinafter referred to as "mixed liquor."
It is, of course, important to quantify the various contaminants in the wastewater. One of those contaminants that is important to quantify is the amount of ammonia. This is because quantification of the amount of ammonia provides valuable information about nitrification/dentrification processes, for example. Various system parameters such as retention time can be altered to enhance the process and increase treatment system efficiency in response to this important information.
A wide variety of methods have been attempted to measure the amount of ammonia in wastewater. However, there have been a number of serious drawbacks in obtaining accurate ammonia quantities on a real time basis. One significant drawback has been the need to filter wastewater samples prior to measuring the amount of ammonia. This is a severe constraint on the real time ability to obtain accurate ammonia readings. Prior art known to the inventors includes the following U.S. Pat. Nos.: 3,354,057; 3,565,583; 3,616,273; 3,877,875; 4,162,195; 4,209,299; 4,216,065; 4,277,343; 4,297,173; 4,666,610; 5,466,604 and 5,641,966.